Motion/still electronic imaging systems including the capability of recording analog motion images and digital still images on the same recording medium, for example 8 mm or VHS format magnetic tape, have recently been developed by a number of manufacturers. The motion/still camcorders currently available record motion images in the same manner as conventional motion only video recording cameras. In order to record still images, the user activates an operator control to switch to a "still" mode of operation in which image data generated from the systems electronic image sensor is temporarily stored in a digital memory for subsequent recording onto videotape.
Conventional motion/still camcorders utilize the same type of NTSC resolution interlaced electronic image sensors originally developed for motion only electronic camera systems. Although the conventional image sensors provide sufficient data to produce relatively low resolution analog NTSC signals, the image sensors are not capable of generating still images having the high resolution associated with high quality electronic still imaging systems. Some current electronic still imaging systems, for example, are capable of recording over one thousand lines of image information, while only 480 lines of image information are required for one frame of an NTSC video signal.
Of course, a high definition television (HDTV) electronic image sensor could be used in a motion/still camcorder to directly obtain high resolution still images and HDTV motion images, but downconversion would be required to obtain NTSC motion images. In such a case, the electronic image sensor must be capable of operating at pixel data rates of greater than 50M pixels/second. Electronic image sensors capable of operating at such high pixel data rates, however, are typically very costly to produce and have much higher power consumption rates than conventional NTSC compatible sensors.
In view of the above, it is an object of the invention to provide an electronic imaging system that is capable of producing NTSC motion images and high resolution still images. It is a further object of the invention to provide an electronic image sensor for the electronic imaging system, which can be operated in a low resolution mode to provide NTSC resolution motion scenes at the standard thirty frames/second rate, and operated in a high resolution mode to provide high resolution still images at slower frame rates. It is a still further object of the invention to provide an electronic image sensor, as described above, that is less expensive to produce and has lower power consumption requirements than HDTV electronic image sensors.